Cryptococcosis was the primary presenting symptom of AIDS in 135 cases in 1983, 279 cases in 1984, and 514 cases in 1985. Upwards of a thousand cases are projected for 1986. Hybridoma technology will be used to add to our library of MAbs directed against Cryptococcus neoformans. Hybridomas of varied epitope specificity will be developed. High affinity IgG antibodies will be obtained by the use of purified polysaccharides, oligosaccharide subunits, conjugated to protein as immunogens. The immunogens will be available from a study already in progress in our laboratories. "Factor" specific antibodies will be obtained from polyclonal sera by employing affinity chromatography. Purified polysaccharides and oligosaccharides, serotypes A, B, C and D, available from a study in process, will be chemically immobilized on agarose. Antibodies in the column effluants and eluates will be analyzed for their epitope specificity. High affinity IgG antibodies will be obtained by the use of the same strategy described above. The epitope specificity of the antibodies will be determined by reliable quantitative enzyme immunoabsorbant assay that has been developed in our laboratories. Both direct and hapten inhibition variations will be used. The reagents produced in this study will be used in our laboratories to probe the structure of the polysaccharides of C. neoformans. Immobilized epitope specific antibody will be used to purify oligosaccharides, prepared by chemical cleavage, according to their epitope structure.